1. Field of the Invention
This invention relates to fiber-forming melt-spinnable aromatic polyesters and to filaments thereof having good tenacity and high modulus.
2. Description of the Prior Art
A class of aromatic polyesters that form optically anisotropic melts from which oriented filaments can be melt spun has been described in Schaefgen et al. U.S. Pat. No. 4,118,372. Most polyesters which are disclosed in this patent are derived primarily from para-oriented dihydric phenols and para-oriented dicarboxylic acids. Filaments that are melt-spun from such polyesters can be heat treated to high tenacity and modulus. Other polyesters are disclosed in the aforementioned Schaefgen et al. patent which are copolymers derived from p-hydroxybenzoic acid, dihydric phenols and dicarboxylic acids.
Recent U.S. Pat. Nos. 4,067,852; 4,083,829; and 4,130,545 disclose polyesters consisting essentially of p-oxybenzoyl moieties, 2,6-dicarboxynaphthalene moieties and various other moieties. U.S. Pat. No. 4,130,545 refers to an application Ser. No. 832,147 which claims an aromatic polyester consisting essentially of p-oxybenzoyl moiety, 2,6-dioxynaphthalene moiety and terephthaloyl moiety. The present invention does not employ a 2,6-dioxynaphthalene moiety. Applicant has found that the new polyesters may be melt spun into filaments which upon heat treatment exhibit good tenacity and high modulus.